Essential Cell Biology 5th edition

CHAPTER ONE
1
Cells: The Fundamental
Units of Life
What does it mean to be living? Petunias, people, and pond scum are all
alive; stones, sand, and summer breezes are not. But what are the fundamental
properties that characterize living things and distinguish them
from nonliving matter?
The answer hinges on a basic fact that is taken for granted now but
marked a revolution in thinking when first established more than 175
years ago. All living things (or organisms) are built from cells: small,
membrane-enclosed units filled with a concentrated aqueous solution of
chemicals and endowed with the extraordinary ability to create copies of
themselves by growing and then dividing in two. The simplest forms of
life are solitary cells. Higher organisms, including ourselves, are communities
of cells derived by growth and division from a single founder cell.
Every animal or plant is a vast colony of individual cells, each of which
performs a specialized function that is integrated by intricate systems of
cell-to-cell communication.
UNITY AND DIVERSITY OF CELLS
CELLS UNDER THE MICROSCOPE
THE PROKARYOTIC CELL
THE EUKARYOTIC CELL
MODEL ORGANISMS
Cells, therefore, are the fundamental units of life. Thus it is to cell biology—the
study of cells and their structure, function, and behavior—that
we look for an answer to the question of what life is and how it works.
With a deeper understanding of cells, we can begin to tackle the grand
historical problems of life on Earth: its mysterious origins, its stunning
diversity produced by billions of years of evolution, and its invasion of
every conceivable habitat on the planet. At the same time, cell biology
can provide us with answers to the questions we have about ourselves:
Where did we come from? How do we develop from a single fertilized egg
cell? How is each of us similar to—yet different from—everyone else on
Earth? Why do we get sick, grow old, and die?